Hydroxylamine is used in many applications; for example in the production of hydroxamated polyacrylamide as described in U.S. Pat. Nos. 4,767,540 and 6,020,418. Hydroxylamine solutions are commercially available under the form of hydroxylamine salts, especially sulfate and chloride salts, or as hydroxylamine free base. By hydroxylamine free base is meant NH2—OH. Hydroxylamine free base is commercially available, for example as a 50% aqueous solution.
However, Applicants have found that when a polyacrylamide water-in-oil microdispersion was reacted with commercially available hydroxylamine free base, the resulting hydroxamated polymer exhibited a low solution viscosity, which made the hydroxamated polymer ineffective as flocculant in the Bayer process. Applicants have discovered that the commercially available hydroxylamine free base solutions contained some hydrazine, presumably as an impurity, and that this hydrazine was responsible for the generation of the reduced solution viscosity of the hydroxamated polymer. Analysis of different lots of 50% aqueous hydroxylamine free base solutions showed that the hydrazine content was in the range of 500-1200 ppm in solution or 1000-2400 ppm relative to hydroxylamine.